This invention relates to a process for preparing titanium dioxide and, more particularly, to an improved process for preparing titanium dioxide by directly hydrolyzing a sulfuric acid solution of ilmenite ore without previously concentrating the acid solution of the ore.
In addition to other uses, titanium dioxide is used in considerable quantities throughout the world as a pigment for paints. In order to be satisfactory for use in this manner, it is important that the particle size of the titanium dioxide be carefully controlled. Accordingly, the prior art has developed procedures for controlling the particle size of titanium dioxide derived from various sources such as the ore ilmenite.
Generally, titanium dioxide is obtained from ilmenite ore by dissolving the ore in a quantity of sulfuric acid and then hydrolyzing the solution to precipitate the titanium dioxide. Frequently, in these procedures, in order to remove ferric sulfate, which is present in the solution, prior to hydrolysis, the solution is concentrated in order that there will be more than 200 grams/liter of titanium oxide present and then the concentrated solution hydrolyzed. This procedure of first concentrating the titanium oxide solution prior to hydrolysis is particularly important also because it has been found that without this prior concentration, the titanium dioxide which is obtained is not generally of good quality and suitable for use as a pigment since its particle size cannot be controlled.
It is accordingly an object of the present invention to produce titanium dioxide of carefully controlled particle size suitable for use as a pigment using a technique which not only results in superior properties for the titanium dioxide, but avoids the practice recognized in the prior art for first concentrating the titanium dioxide in acid solution prior to hydrolysis.